Electro-permanent magnetic devices are used in industrial systems, for example, to magnetically clamp objects securely without fear of loss of magnetic clamping force due to power failures. Applications include holding workpieces during machining, holding dies/molds in presses, lifting, transporting, etc.
The magnetic circuit of an electro-permanent magnetic device includes an electro-permanent magnet that can be electrically switched between On (magnetized) and Off (de-magnetized) states, and once in either state, no further electrical energy is required to maintain the electro-permanent magnet in that state. Once energized, the electro-permanent magnet can thus be disconnected from electrical power indefinitely without losing magnetic clamping power.
The ability to disconnect an electro-permanent magnetic device from power without losing magnetic clamping power is valuable because it allows a part to be loaded on an electro-permanent magnetic chuck, and then the chuck can be disconnected from power and moved through multiple processing stations without the need of an electrical connection being maintained with the chuck and without fear of losing holding power.
In a double magnet DM device, permanent magnets and switching magnets are used together so that the switching magnets can be programmed in a first polarity to turn the DM device on (so that magnetic energy of the permanent and switching magnets combine) and so that the switching magnets can be programmed in a second polarity to turn the DM device off (so that magnetic energy of the permanent and switching magnets cancel). In the on state, the combined magnetic energies of the permanent and switching magnets flow out of the device to hold a workpiece. In the off state, magnetic energy of the permanent and switching magnets are trapped in the device so that the workpiece may be released.
When the DM device is turned off, however, the workpiece may remain partly magnetized, and the residual magnetism in the workpiece may create a weak magnetic circuit, making the workpiece difficult to remove from the DM device even though the magnetism has been turned off.